Li Nuclei Research Articles

Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is based on the nuclear reaction that ~(10)B is irradiated with neutrons of the appropriate energy to produce high-energy alpha particles and recoiling ~7Li nuclei. BNCT has been used clinically to treat patients with glioma and melanoma. It is reviewed that the principles of BNCT, tumor-targeted boron delivery agents, neutron sources, results of clinical trails, and it is discussed that the challenges and problems that must be faced if BNCT is to become a useful treatment modality for tumors.

Measurement of the diffusion of multiple nuclei in restricted spaces by pulsed field gradient NMR

In this study, the restricted diffusion of a solvent, anion, and cation in an electrolyte solution was measured by pulsed field gradient (PFG) NMR for 1H, 19F, and 7Li nuclei. Further, the time dependences of the diffusion coefficients were measured for a 1 M LiPF6 electrolyte solution in porous polyethylene, which has pores with sizes of tens of micrometers. The decreasing ratio of the diffusion coefficients of the solvent, cation, and anion based on the diffusion time can be scaled similarly for each diffusion distance. The experimentally obtained time dependences of the diffusion coefficients of the solvent, anion, and cation agreed with the results of the analytical equation with the same structural parameters. Furthermore, the abovementioned experimental results were produced via Monte Carlo simulation in the same model-restricted structure for the solvent, anion, and cation. Based on PFG-NMR, it can be concluded that the solvent, anion, and cation exhibit the same restricted diffusion behavior in polyethylene pores measuring tens of micrometers. It was confirmed that measuring the time dependences of the diffusion coefficients via PFG-NMR with multiple nuclei is effective for studying the diffusion mechanisms of electrolyte solutions in restricted spaces.

Asymptotic characteristics of decay channels of states of light nuclei in the ab initio approach

A new convenient method for precise theoretical calculations of quantities of traditional theory of nuclear reactions such as widths of resonances (including sub-threshold), and asymptotic normalization coefficients is proposed. This method may be considered as a step on the road to full theoretical ab initio description of light nuclei spectroscopic data. As an illustration of this method the computational results for all relevant two-body channels for all known and some theoretically predicted states of 7Li nucleus are shown. Well-proven on a large amount of data Daejeon16 potential was used in the calculations. The most part of the results turn out to be in a good agreement with the experimental data contained in spectroscopic tables.

Use of Microscopic Theoretical Methods for The Construction of The Nuclear Wavefunction of 7Li

Microscopic theoretical studies of scattering and reaction problems for light nuclei have been extensively carried out using resonating group method. In this paper we have used the nuclear cluster model, the resonating group method, the generator coordinate method and complex generator coordinate technique for the construction of microscopic antisymmetrized nuclear wavefunction of 7Li nucleus. This wavefunction can be further used to calculate the structural properties of the nucleus. The 7Li nucleus in ground state is considered as a nuclear system consisting of three clusters namely an alpha cluster, a deuteron cluster and a neutron cluster. We have chosen spatial, spin and isospin function of cluster internal functions. The arguments of internal wavefunction include the parameter coordinates. These parameters can be adjusted to some extent to obtain predictions close to experimental results. The wavefunction is written using shell model with definite parity and angular momentum. The complex generator coordinate technique allows this wavefunction to write it as an antisymmetrized product of seven single particle functions after inclusion of the wavefunction for the center- of -mass motion

Effect of Cluster Polarization on the Spectrum of the \(^6\)Li Nucleus

Effect of Cluster Polarization on the Spectrum of the \(^6\)Li Nucleus

Reaction dynamics of exotic and stable weakly-bound nuclei using a four-body continuum-discretized coupled-channels formalism

Reactions induced by four weakly-bound nuclei on a lead target, at energies around the Coulomb barrier, are described using the same four-body continuum-discretized coupled-channels formalism. The nuclei considered are the halo nuclei 11Li and 6He, the stable nucleus 9Be and the proton-rich nucleus 10C. The differences and similarities on the reaction dynamics are addressed.

Root Mean Square Radius of 6Li Nucleus using Cluster Model Wavefunction

The calculation of root mean square nuclear charge radius is one of the most important nuclear parameters regarding the size and structure of the nucleus. In this paper calculations for root mean square (r.m.s.) radius of the ground state of 6Li nucleus using high energy electron scattering is presented. The initial work involves writing first the cluster model wavefunction employing the resonating group method, generator coordinate method and complex generator coordinate technique. The wavefunction is written with definite parity, spin, total angular momentum and relative motion between the alpha cluster and deuteron cluster and the center-of-mass of the two clusters. The application of complex generator coordinate technique transforms the cluster model wavefunction into antisymmetrized products of single particle wavefunction written in terms of single particle co-ordinates, the centerof-mass coordinates, parameter coordinates and generator coordinates. The width parameters of alpha and deuteron clusters are adjusted to obtain predictions close to experimental values.

APPLICATION OF TWO-CLUSTER MICROSCOPIC MODEL TO STUDY PROCESSES ASSOCIATED WITH THE COSMOLOGICAL LITHIUM PROBLEM

This paper presents the results of studies of long-lived resonance states of the 6Li nucleus and the radiative capture reaction leading to the synthesis of 6Li. In connection with the importance of the lithium problem for the fields of nuclear physics and nuclear astrophysics, the reactions of primary nucleosynthesis are of great interest for studies and consideration using new calculation methods. Cluster models are a powerful tool for theoretical analysis and solution of this problem. One of these models is the microscopic cluster model, or a method known as the algebraic version of the resonant group method (AVRGM), which will allow us to investigate this problem from a new angle and obtain data on resonance states. For this task, a modified Hasegawa-Nagata potential was chosen, which has its own unique characteristics and exchange parameters. The obtained data were compared with experimental data and it was shown that they showed good agreement, and the applicability of this technique to the description of similar reactions that originate in the first three minutes after the birth of the universe.

Analysis of strong refractive effect within 11Li projectile structure

In the context of the double folding optical model, the strong refractive effect for elastic scattering of 11Li + 12C and 11Li + 28Si systems at incident energies of 29, 50, and 60 MeV/n is studied. Real folded potentials are generated based on a variety of nucleon-nucleon interactions with the suggested density distributions for the halo structure of 11Li nuclei. The rearrangement term (RT) of the extended realistic density dependent CDM3Y6 effective interaction is considered. The imaginary potential was taken in the traditional standard Woods-Saxon form. Satisfactory results for the calculated potentials are obtained, with a slight effect of the RT in CDM3Y6 potential. Successful reproduction with a normalization factor close to one for the observed angular distributions of the elastic scattering differential cross section has been achieved using the derived potentials. The obtained reaction cross-section is studied as a guide by extrapolating our calculations and previous results.

Sensitivity of core+n potential on configuration mixing in ground state of neutron-rich exotic nuclei

We study the configuration mixing in the ground state of the neutron-rich exotic nuclei. The results for weakly-bound two-neutron halo nuclei 11Li and 22C, and the two-neutron unbound nucleus 26O are reported. For the present study, we use a three-body (core + n + n) structure model developed for describing the two-neutron halo system by explicit coupling of unbound continuum states of the subsystem (core + n). We use a density-dependent contact-delta interaction to describe the neutron-neutron interaction and its strength is varied to fix the binding energy. We report the two-neutron correlations in the ground state of these systems.

Neutron Response of the EJ-254 Boron-Loaded Plastic Scintillator

Organic scintillators doped with capture agents provide a detectable signal for neutrons over a broad energy range. This work characterizes the fast and slow neutron response of EJ-254, an organic plastic scintillator with 5% natural boron loading by weight. For fast neutrons, the primary mechanism for light generation in organic scintillators is n-p elastic scattering. To study the fast neutron response, the proton light yield of EJ-254 was measured at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. Using a broad-spectrum neutron source and a double time-of-flight technique, the EJ-254 proton light yield was obtained over the energy range of approximately 270 keV to 4.5 MeV and determined to be in agreement with other plastic scintillators comprised of the same polymer base. To isolate the slow neutron response, an AmBe source with polyethylene moderator was made incident on the EJ-254 scintillator surrounded by an array of EJ-309 observation detectors. Events in the EJ-254 target coincident with the signature 477.6 keV $\gamma$ ray (resulting from deexcitation of the residual $^{7}$Li nucleus following boron neutron capture) were identified. Pulse shape discrimination was used to evaluate the temporal differences in the response of EJ-254 scintillation signals arising from $\gamma$-ray and fast/slow neutron interactions. Clear separation between $\gamma$-ray and fast neutrons signals was not achieved and the neutron capture feature was observed to overlap both the $\gamma$-ray and fast neutron bands. Taking into account the electron light nonproportionality, the neutron-capture light yield in EJ-254 was determined to be 89.4$\pm$1.1 keVee.

(Battery Division Postdoctoral Associate Research Award Address Sponsored by MTI Corporation and the Jiang Family Foundation) Li Plating During Fast Charge: Detection and Prevention

Enabling fast charge of lithium-ion batteries is an essential step towards the wider adoption of electric vehicles. A key challenge is that high charging currents can promote several aging mechanisms, including lithium plating on the graphite anode. There is research suggesting that the deposition of metallic lithium favors further Li plating in a self-reinforcing loop, which can eventually lead to sudden cell failure.[1] Hence, detecting Li deposition during the early stages and developing electrochemical cycling protocols that avoid plating conditions are crucial to enabling fast-charge.In this talk we will discuss two approaches to investigate Li deposition. The first one is through detection. Our group has demonstrated that plated Li can intensify the Raman signal of its surrounding SEI, which then serves as an indirect marker for the presence of Li nuclei.[2] The sensitivity of this technique enables the study of where Li will tend to plate, and how this deposition evolves spatially over the course of many cycles. The second approach is through the use of a reference electrode, which can be used to estimate electrode potentials during fast charging.[3] This capability supports the development of fast-charging protocols that optimize time utilization while steering the cells away from Li plating conditions. Examples of such cycling protocols will be discussed during the presentation.

Initial Stage of Li Electrodeposition in PC Electrolyte

Li metal is an attractive material for negative electrode because it has the highest energy density (about 3600 mA h g-1). However, the Li metal dendrite is easily formed during the charging process. Its growth induces significantly poor electrochemical reversibility due to so-called dead Li and even imposes a risk of short-circuit phenomenon followed by firing or even fatal explosion accidents. Considerable efforts have been made so far in elucidating and suppressing Li dendrite formation toward practical utilization of Li metal anode(1). As well known, many studies were published on the dendrite formation of metals such as Ag, Cu and Zn formed in the course of electrodeposition in aqueous electrolyte. Metal electrodeposition in aqueous electrolyte was studied by Volmer, Kossel, Stranski and Frank. They described that the nucleation and growth phenomena proceed through the surface diffusion of adatoms on the substrate followed by its aggregation and incorporation at the interface of growing nuclei(2). Nucleation process has been considered to be one of the most important stages for morphological variations of the deposits. Since Li metal is generally electrodeposited in organic electrolytes because of electrochemical window restriction, the Li deposition essentially accompanies the adsorption or decomposition of the organic species on the substrate and deposited Li metal. Characteristics of so-called SEI strongly influences the charge transfer kinetics, which affects the nucleation and consequently the morphological variations. In this regard, the Li deposition process accompanying SEI formation is considered to be fundamentally different from that of metal deposition in aqueous solution. In fact, recent work revealed that Li deposition proceeded underneath SEI(3). Also, TEM observations indicated the competitive deposition on tip and root of Li dendrite(4). In this study, we focused on the investigation of Li nucleation behavior during electrodeposition in a common propylene carbonate (PC) electrolyte by applying the double-pulsed potential technique which has been widely used for analyzing the nucleation and growth of electrochemical process. We have tried to separately control the nucleation phenomena from the growth process during the morphological variations develop to dendrite formation. Accordingly, our interest is focused to associate the surface morphological change with the Li nucleation behavior. The double-pulsed technique used in ionic liquid electrolyte(5) was also applied to the present organic PC work. The electrolyte composed of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and PC. Water content of the electrolyte was confirmed by Kirl-Fisher titration (< 20 ppm). Electrochemical measurement was conducted with a typical three electrode cell in Ar glove box (dew point < -90 ℃), varying the pulse condition, salt concentration and temperature. A mechanically polished cross-section of Ni wire (500 μm in diameter, Nilaco Corp.) was used as the working electrode. A lithium foil (200 μm in thickness, Honjo Metal Co., Ltd.) was used as the counter electrode and the reference electrode. The working electrode was immersed in dimethyl carbonate and dried in vacuum after electrolysis, followed by SEM observation of deposits. Fig.1 shows a typical example of chronoamperograms after applying double pulse potential. (The inset shows the time transient in the initial stage). When the first potential of -100 mV is applied, large currents flow in the beginning, which is attributed to the charging of double layer capacitance, the reduction of surface oxide layer and SEI formation. The current then decreases toward the minimum value and starts increasing again, which should correspond to the nucleation and growth. After the interruption of the first potential at 5 s, the formed Li nuclei grow moderately at the second potential of -15 mV. The gradual increase of current after 500 s is probably caused by the enlargement of effective surface area associated with nucleus growth. SEM images of the resultant deposits are shown in Fig.2. Granular deposits with the size of about 1-3 μm are relatively homogeneously distributed. Nucleation behaviors under various experimental conditions will be discussed with the results of SEM observations and electrochemical measurements.References D. Lin, Y. Liu, Y. Cui, Nature Energy, 12, 194–206 (2017).E. Budevski, G. Staikov and W. J. Lorenz, Electrochim. Acta, 45, 2559-2574 (2000).A. Jana, R. E. García, Nano Energy, 41, 552–565 (2017).Y. Li, Y. Yu et al., Science, 358, 506–510 (2017).T. Nishida, K. Nishikawa, M. Rosso and Y. Fukunaka, Electrochim. Acta, 100, 333-341 (2013). Figure 1

Deuteron inelastic scattering on 6Li and 7Li nuclei within the three-body cluster model * *The reported study was funded by RFBR, (20-02-00004)

The problem of the deuteron interaction with lithium nuclei, treated as a system of two coupled pointlike clusters, is formulated to calculate the cross sections of the d+Li reaction. The d+Li reaction mechanism is described using the Faddeev theory for the three-body problem of deuteron-nucleus interaction. This theory is slightly extended for calculation of the stripping processes 6Li(d,p)7Li, 7Li(d,p)8Li, 6Li(d,n)7Be, and 7Li(d,n)8Be, as well as fragmentation reactions yielding tritium, -particles, and continuous neutrons and protons in the initial deuteron kinetic-energy region MeV. The phase shifts found for Li and Li elastic scattering, as part of the simple optic model with a complex central potential, were used to find the cross sections for the 6Li and 7Li radiation captures. The three-body dynamics role is also summarized to demonstrate its significant influence within the Li system.

Highly efficient lithium utilization in lithium metal full-cell by simulated missile guidance and confinement systems

The efficient utilization of metallic lithium (Li) is the key to enable application of Li metal full-cell with low amount of excess Li, contributing to higher safety and energy density. Herein, we report an extraordinary Li metal full-cell with only 20% excess Li, which demonstrated significantly improved reversibility and high Coulombic efficiency. Ingenious simulated missile guidance and confinement system (SMGCS) was designed to guide and confine Li deposition through constructing compatible silver lithiophilic sites and nitrate layer. Silver sites act as effective Li nuclei to attract Li ions and direct the initial nucleation. The generated nitrate layer affords an interfacial environment favorable for confined and uniform deep Li deposition, which is theoretically verified by molecular dynamics (MD) simulations. The two combined merits offer a robust and dendrite-free Li deposition, enabling the application of Li metal full-cell with slight excess Li. They also result in an outperformed Li cycling efficiency of ca. 99% for over 300 cycles along with deep cycling at a high capacity of 10 mA h cm−2 in carbonate electrolytes. The unprecedented high degree of Li utilization opens a new avenue for the future development of highly efficient Li metal full cells.

Precision Calculation of Hyperfine Structure and the Zemach Radii of ^{6,7}Li^{+} Ions.

The hyperfine structures of the 2^{3}S_{1} states of the ^{6}Li^{+} and ^{7}Li^{+} ions are investigated theoretically to extract the Zemach radii of the ^{6}Li and ^{7}Li nuclei by comparing with precision measurements. The obtained Zemach radii are larger than the previous values of Puchalski and Pachucki [Phys. Rev. Lett. 111, 243001 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.243001] and disagree with them by about 1.5 and 2.2 standard deviations for ^{6}Li and ^{7}Li, respectively. Furthermore, our Zemach radius of ^{6}Li differs significantly from the nuclear physics value, derived from the nuclear charge and magnetic radii [Phys. Rev. A 78, 012513 (2008)PLRAAN1050-294710.1103/PhysRevA.78.012513] by more than 6σ, indicating an anomalous nuclear structure for ^{6}Li. The conclusion that the Zemach radius of ^{7}Li is about 40% larger than that of ^{6}Li is confirmed. The obtained Zemach radii are used to calculate the hyperfine splittings of the 2^{3}P_{J} states of ^{6,7}Li^{+}, where an order of magnitude improvement over the previous theory has been achieved for ^{7}Li^{+}.

Studying the Cluster Structure of the 11B Nucleus

Excitation spectra of the 11В nucleus in the lithium reaction of deuteron and α-particle cluster transfer are calculated by summing corresponding spectroscopic S-factors in the multiparticle shell model. It is shown that the difference between the excitation spectra of the 11В nucleus in lithium reactions of α-cluster transfer on the 7Li nucleus and the reaction of 7Li(α, γ)11B radiative capture is due to specific structural features of the states of the 11В nucleus in the near-threshold region.

Cluster Structure of 10B Nucleus Levels

The excitation spectra of the 10В nucleus in the lithium reactions of triton and α-particle cluster transfer were calculated via summation of the corresponding spectroscopic S-factors within the multiparticle shell model. It is shown that the difference between the excitation spectra of the 10В nucleus in the lithium reactions of α-cluster transfer on 6Li nucleus and in the reaction of 6Li(α, γ)10B radiative capture is due to structural features of the states of the 10В nucleus in the near-threshold region.

Hydration and Diffusion of H+, Li+, Na+, Cs+ Ions in Cation-Exchange Membranes Based on Polyethylene- and Sulfonated-Grafted Polystyrene Studied by NMR Technique and Ionic Conductivity Measurements.

The main particularities of sulfonate groups hydration, water molecule and alkaline metal cation translation mobility as well as ionic conductivity were revealed by NMR and impedance spectroscopy techniques. Cation-exchange membranes MSC based on cross-linked sulfonated polystyrene (PS) grafted on polyethylene with ion-exchange capacity of 2.5 mg-eq/g were investigated. Alkaline metal cation hydration numbers (h) calculated from temperature dependences of 1H chemical shift of water molecule for membranes equilibrated with water vapor at RH = 95% are 5, 6, and 4 for Li+, Na+, and Cs+ ions, respectively. These values are close to h for equimolar aqueous salt solutions. Water molecules and counter ions Li+, Na+, and Cs+ diffusion coefficients were measured by pulsed field gradient NMR on the 1H, 7Li, 23Na, and 133Cs nuclei. For membranes as well as for aqueous chloride solutions, cation diffusion coefficients increased in the following sequence: Li+ < Na+ < Cs+. Cation and water molecule diffusion activation energies in temperature range from 20 °C to 80 °C were close to each other (about 20 kJ/mol). The cation conductivity of MSC membranes is in the same sequence, Li+ < Na+ < Cs+ << H+. The conductivity values calculated from the NMR diffusion coefficients with the use of the Nernst–Einstein equation are essentially higher than experimentally determined coefficients. The reason for this discrepancy is the heterogeneity of membrane pore and channel system. Ionic conductivity is limited by cation transfer in narrow channels, whereas the diffusion coefficient characterizes ion mobility in wide pores first of all.

Synthesis of enriched boron nitride nanocrystals: A potential element for biomedical applications

The shortcomings in Boron neutron capture therapy (BNCT) and Hyperthermia for killing the tumor cell desired for the synthesis of a new kind of material suitable to be first used in BNCT and later on enable the conditions for Hyperthermia to destroy the tumor cell. The desire led to the synthesis of large band gap semiconductor nano-size Boron-10 enriched crystals of hexagonal boron nitride (10BNNCs). The contents of 10BNNCs are analyzed with the help of x-ray photoelectron spectroscopy (XPS) and counter checked with Raman and XRD. The 10B-contents in 10BNNCs produce 7Li and 4He nuclei. A Part of the 7Li and 4He particles released in the cell is allowed to kill the tumor (via BNCT) whereas the rest produce electron-hole pairs in the semiconductor layer of 10BNNCs suggested to work in Hyperthermia with an externally applied field.